Modify GUI for better readability, clean up

src/algorithms/edmonds_karp.rs

@@ -0,0 +1,5 @@
+// Edmonds-Karp (also Ford-Fulkerson mit BFS statt DFS),
+
+//pub fn edmonds_karp(mut graph: StableGraph<(f32, f32), (u64, u64)>, source: NodeIndex, sink: NodeIndex) -> StableGraph<(f32, f32), (u64, u64)> {
+//
+//}

src/algorithms/ford_fulkerson.rs

@@ -1,11 +1,9 @@
-use std::cmp::min;
-use std::collections::VecDeque;
-
-use eframe::glow::FALSE;
 // Ford-Fulkerson mit DFS zur Berechnung des flusserhöhenden Pfades,
 // Edmonds-Karp (also Ford-Fulkerson mit BFS statt DFS),
 // Dinic
 // Goldberg-Tarjan (auch Preflow-Push oder Push-Relabel genannt).
+use std::cmp::min;
+use std::collections::VecDeque;
 use egui_graphs::{Graph, DefaultNodeShape, DefaultEdgeShape};
 use petgraph::adj::EdgeIndex;
 use petgraph::data::Build;
@@ -15,7 +13,6 @@ use petgraph::visit::{Dfs, EdgeRef, NodeRef, VisitMap, Visitable};
 use petgraph::stable_graph::{StableGraph, NodeIndex};
 
 use crate::random_generator::MaxflowProblem;
-use crate::graph::{MaxflowNode, MaxflowEdge};
 //mod random_generator;
 
 fn available_capacity(edge: EdgeReference<'_, (u64, u64)>) -> u64 {
@@ -76,12 +73,12 @@ pub fn ford_fulkerson(mut graph: StableGraph<(f32, f32), (u64, u64)>, source: No
     graph
 }
 
-pub struct FordFulkerson {
+//pub struct FordFulkerson {
-    problem: MaxflowProblem,
+//    problem: MaxflowProblem,
-    flows: Graph<(), u64, Directed, u32, DefaultNodeShape, DefaultEdgeShape>,
+//    flows: Graph<(), u64, Directed, u32, DefaultNodeShape, DefaultEdgeShape>,
     // alertnatively, use a map from EdgeIndex to flow value
     //dfs: Dfs<N, VM>,
-}
+//}
 
 /* impl FordFulkerson {
     fn new(problem: MaxflowProblem) -> S/elf {

src/algorithms/mod.rs

@@ -0,0 +1,4 @@
+mod edmonds_karp;
+mod ford_fulkerson;
+
+pub use ford_fulkerson::ford_fulkerson;

src/graph.rs

@@ -1,33 +0,0 @@
-//use egui_graphs::{Node, Edge};
-use petgraph::graph::{Node, Edge};
-
-pub trait MaxflowNode {
-    fn visited(&self) -> bool;
-    fn set_visited(&mut self, b: bool);
-}
-
-pub trait MaxflowEdge {
-    fn remaining_capacity(&self) -> u64;
-    fn set_capacity(&mut self, c: u64);
-}
-
-/* impl MaxflowNode for Node<bool, (u64, u64)> {
-    fn visited(&self) -> bool {
-        *self.()
-    }
-
-    fn set_visited(&mut self, b: bool) {
-        let payload = self.payload_mut();
-        *payload = b;
-    }
-} */
-
-impl MaxflowEdge for Edge<(u64, u64)> {
-    fn remaining_capacity(&self) -> u64 {
-        self.weight.1 - self.weight.0
-    }
-
-    fn set_capacity(&mut self, c: u64) {
-        self.weight.0 = c;
-    }
-}

src/layout.rs

@@ -0,0 +1,355 @@
+use std::f32::consts::PI;
+
+use egui::{
+    epaint::{CubicBezierShape, QuadraticBezierShape},
+    Color32, Pos2, Stroke, Vec2, Shape, FontId, FontFamily, epaint::{TextShape}
+};
+
+use petgraph::{matrix_graph::Nullable, stable_graph::IndexType, EdgeType};
+
+use egui_graphs::{
+    DefaultEdgeShape, DisplayEdge, EdgeProps,
+    DefaultNodeShape, DisplayNode, NodeProps,
+    Node, DrawContext
+};
+
+
+#[derive(Clone)]
+pub struct CustomEdgeShape {
+    pub order: usize,
+    pub selected: bool,
+
+    pub width: f32,
+    pub tip_size: f32,
+    pub tip_angle: f32,
+    pub curve_size: f32,
+    pub loop_size: f32,
+    pub label_text: String,
+}
+
+impl<E: Clone> From<EdgeProps<E>> for CustomEdgeShape {
+    fn from(props: EdgeProps<E>) -> Self {
+        Self {
+            order: props.order,
+            selected: props.selected,
+            label_text: props.label,
+
+            width: 1.,
+            tip_size: 10.,
+            tip_angle: std::f32::consts::TAU / 30.,
+            curve_size: 15.,
+            loop_size: 3.,
+        }
+    }
+}
+
+impl<N: Clone, E: Clone, Ty: EdgeType, Ix: IndexType, D: DisplayNode<N, E, Ty, Ix>>
+    DisplayEdge<N, E, Ty, Ix, D> for CustomEdgeShape
+{
+    // helper functions
+    // copied from: https://github.com/SeverinAlexB/pknames/blob/d042b6843ee503d92ae36742bab81b14574d9ad3/cli/src/visualization/edge_vis.rs
+    fn is_inside(
+        &self,
+        start: &Node<N, E, Ty, Ix, D>,
+        end: &Node<N, E, Ty, Ix, D>,
+        pos: egui::Pos2,
+    ) -> bool {
+        if start.id() == end.id() {
+            return is_inside_loop(start, self, pos);
+        }
+
+        let pos_start = start.location();
+        let pos_end = end.location();
+
+        if self.order == 0 {
+            return is_inside_line(pos_start, pos_end, pos, self);
+        }
+
+        is_inside_curve(start, end, self, pos)
+    }
+
+    fn shapes(
+        &mut self,
+        start: &Node<N, E, Ty, Ix, D>,
+        end: &Node<N, E, Ty, Ix, D>,
+        ctx: &DrawContext,
+    ) -> Vec<egui::Shape> {
+        // fixed properties
+        let edge_color = Color32::LIGHT_GRAY;
+        let label_color = Color32::DARK_GRAY;
+        //let label_visible = true;
+        //let style = ctx.ctx.style().visuals.widgets.inactive;
+
+        // calculate coordinates
+        let dir = (end.location() - start.location()).normalized();
+        let start_connector_point = start.display().closest_boundary_point(dir);
+        let end_connector_point = end.display().closest_boundary_point(-dir);
+        let tip_end = end_connector_point;
+        let edge_start = start_connector_point;
+        let edge_end = end_connector_point;
+
+        // draw curved edge
+        let stroke_edge = Stroke::new(self.width * ctx.meta.zoom, edge_color);
+        let dir_perpendicular = Vec2::new(-dir.y, dir.x);
+        let center_point = (edge_start + edge_end.to_vec2()).to_vec2() / 2.;
+        let control_point = (center_point + dir_perpendicular * self.curve_size as f32).to_pos2();
+        let tip_dir = (control_point-tip_end).normalized();
+        //println!("edge_start: {:?} edge_end {:?} center_point {:?} dir_p {:?} control_point {:?}", edge_start, edge_end, center_point, dir_perpendicular, control_point);
+
+        let arrow_tip_dir_1 = rotate_vector(tip_dir, self.tip_angle) * self.tip_size;
+        let arrow_tip_dir_2 = rotate_vector(tip_dir, -self.tip_angle) * self.tip_size;
+        let tip_start_1 = tip_end + arrow_tip_dir_1;
+        let tip_start_2 = tip_end + arrow_tip_dir_2;
+
+        let edge_end_curved = point_between(tip_start_1, tip_start_2);
+        let line_curved = QuadraticBezierShape::from_points_stroke(
+            [
+                ctx.meta.canvas_to_screen_pos(edge_start),
+                ctx.meta.canvas_to_screen_pos(control_point),
+                ctx.meta.canvas_to_screen_pos(edge_end_curved),
+            ],
+            false,
+            Color32::TRANSPARENT,
+            stroke_edge,
+        );
+
+        // draw tip/arrow
+        let stroke_tip = Stroke::new(0., edge_color);
+        let line_curved_tip = Shape::convex_polygon(
+            vec![
+                ctx.meta.canvas_to_screen_pos(tip_end),
+                ctx.meta.canvas_to_screen_pos(tip_start_1),
+                ctx.meta.canvas_to_screen_pos(tip_start_2),
+            ],
+            edge_color,
+            stroke_tip,
+        );
+
+
+        // draw label
+        let size = (::egui_graphs::node_size(start, dir) + egui_graphs::node_size(end, dir)) / 2.;
+        let galley = ctx.ctx.fonts(|f| {
+            f.layout_no_wrap(
+                self.label_text.clone(),
+                FontId::new(ctx.meta.canvas_to_screen_size(size), FontFamily::Monospace),
+                label_color,
+            )
+        });
+
+        let flattened_curve = line_curved.flatten(None);
+        let median = *flattened_curve.get(flattened_curve.len() / 2).unwrap();
+
+        let label_width = galley.rect.width();
+        let label_height = galley.rect.height();
+        let pos = Pos2::new(median.x - label_width / 2., median.y - label_height);
+
+        let label_shape = TextShape::new(pos, galley, label_color);
+        
+        vec![line_curved.into(), line_curved_tip, label_shape.into()]
+    }
+
+    fn update(&mut self, state: &egui_graphs::EdgeProps<E>) {
+        self.order = state.order;
+        self.selected = state.selected;
+        self.label_text = state.label.to_string();
+    }
+
+}
+
+// Everything below is copied from:
+// https://github.com/SeverinAlexB/pknames/blob/d042b6843ee503d92ae36742bab81b14574d9ad3/cli/src/visualization/edge_vis.rs
+fn shape_looped(
+    node_size: f32,
+    node_center: Pos2,
+    stroke: Stroke,
+    e: &CustomEdgeShape,
+) -> CubicBezierShape {
+    let center_horizon_angle = PI / 4.;
+    let y_intersect = node_center.y - node_size * center_horizon_angle.sin();
+
+    let edge_start = Pos2::new(
+        node_center.x - node_size * center_horizon_angle.cos(),
+        y_intersect,
+    );
+    let edge_end = Pos2::new(
+        node_center.x + node_size * center_horizon_angle.cos(),
+        y_intersect,
+    );
+
+    let loop_size = node_size * (e.loop_size + e.order as f32);
+
+    let control_point1 = Pos2::new(node_center.x + loop_size, node_center.y - loop_size);
+    let control_point2 = Pos2::new(node_center.x - loop_size, node_center.y - loop_size);
+
+    CubicBezierShape::from_points_stroke(
+        [edge_end, control_point1, control_point2, edge_start],
+        false,
+        Color32::default(),
+        stroke,
+    )
+}
+
+fn shape_curved(
+    pos_start: Pos2,
+    pos_end: Pos2,
+    size_start: f32,
+    size_end: f32,
+    stroke: Stroke,
+    e: &CustomEdgeShape,
+) -> QuadraticBezierShape {
+    let vec = pos_end - pos_start;
+    let dist: f32 = vec.length();
+    let dir = vec / dist;
+
+    let start_node_radius_vec = Vec2::new(size_start, size_start) * dir;
+    let end_node_radius_vec = Vec2::new(size_end, size_end) * dir;
+
+    let tip_end = pos_start + vec - end_node_radius_vec;
+
+    let edge_start = pos_start + start_node_radius_vec;
+    let edge_end = pos_end + end_node_radius_vec;
+
+    let dir_perpendicular = Vec2::new(-dir.y, dir.x);
+    let center_point = (edge_start + tip_end.to_vec2()).to_vec2() / 2.0;
+    let control_point =
+        (center_point + dir_perpendicular * e.curve_size * e.order as f32).to_pos2();
+
+    QuadraticBezierShape::from_points_stroke(
+        [edge_start, control_point, edge_end],
+        false,
+        stroke.color,
+        stroke,
+    )
+}
+
+fn is_inside_loop<E: Clone, N: Clone, Ix: IndexType, Ty: EdgeType, D: DisplayNode<N, E, Ty, Ix>>(
+    node: &Node<N, E, Ty, Ix, D>,
+    e: &CustomEdgeShape,
+    pos: Pos2,
+) -> bool {
+    let node_size = node_size(node);
+
+    let shape = shape_looped(node_size, node.location(), Stroke::default(), e);
+    is_point_on_cubic_bezier_curve(pos, shape, e.width)
+}
+
+fn is_inside_line(pos_start: Pos2, pos_end: Pos2, pos: Pos2, e: &CustomEdgeShape) -> bool {
+    let distance = distance_segment_to_point(pos_start, pos_end, pos);
+    distance <= e.width
+}
+
+fn is_inside_curve<
+    N: Clone,
+    E: Clone,
+    Ty: EdgeType,
+    Ix: IndexType,
+    D: DisplayNode<N, E, Ty, Ix>,
+>(
+    node_start: &Node<N, E, Ty, Ix, D>,
+    node_end: &Node<N, E, Ty, Ix, D>,
+    e: &CustomEdgeShape,
+    pos: Pos2,
+) -> bool {
+    let pos_start = node_start.location();
+    let pos_end = node_end.location();
+
+    let size_start = node_size(node_start);
+    let size_end = node_size(node_end);
+
+    let shape = shape_curved(
+        pos_start,
+        pos_end,
+        size_start,
+        size_end,
+        Stroke::default(),
+        e,
+    );
+    is_point_on_quadratic_bezier_curve(pos, shape, e.width)
+}
+
+fn node_size<N: Clone, E: Clone, Ty: EdgeType, Ix: IndexType, D: DisplayNode<N, E, Ty, Ix>>(
+    node: &Node<N, E, Ty, Ix, D>,
+) -> f32 {
+    let left_dir = Vec2::new(-1., 0.);
+    let connector_left = node.display().closest_boundary_point(left_dir);
+    let connector_right = node.display().closest_boundary_point(-left_dir);
+
+    (connector_right.x - connector_left.x) / 2.
+}
+
+/// Returns the distance from line segment `a``b` to point `c`.
+/// Adapted from https://stackoverflow.com/questions/1073336/circle-line-segment-collision-detection-algorithm
+fn distance_segment_to_point(a: Pos2, b: Pos2, point: Pos2) -> f32 {
+    let ac = point - a;
+    let ab = b - a;
+
+    let d = a + proj(ac, ab);
+
+    let ad = d - a;
+
+    let k = if ab.x.abs() > ab.y.abs() {
+        ad.x / ab.x
+    } else {
+        ad.y / ab.y
+    };
+
+    if k <= 0.0 {
+        return hypot2(point.to_vec2(), a.to_vec2()).sqrt();
+    } else if k >= 1.0 {
+        return hypot2(point.to_vec2(), b.to_vec2()).sqrt();
+    }
+
+    hypot2(point.to_vec2(), d.to_vec2()).sqrt()
+}
+
+/// Calculates the square of the Euclidean distance between vectors `a` and `b`.
+fn hypot2(a: Vec2, b: Vec2) -> f32 {
+    (a - b).dot(a - b)
+}
+
+/// Calculates the projection of vector `a` onto vector `b`.
+fn proj(a: Vec2, b: Vec2) -> Vec2 {
+    let k = a.dot(b) / b.dot(b);
+    Vec2::new(k * b.x, k * b.y)
+}
+
+fn is_point_on_cubic_bezier_curve(point: Pos2, curve: CubicBezierShape, width: f32) -> bool {
+    is_point_on_bezier_curve(point, curve.flatten(Option::new(10.0)), width)
+}
+
+fn is_point_on_quadratic_bezier_curve(
+    point: Pos2,
+    curve: QuadraticBezierShape,
+    width: f32,
+) -> bool {
+    is_point_on_bezier_curve(point, curve.flatten(Option::new(0.3)), width)
+}
+
+fn is_point_on_bezier_curve(point: Pos2, curve_points: Vec<Pos2>, width: f32) -> bool {
+    let mut previous_point = None;
+    for p in curve_points {
+        if let Some(pp) = previous_point {
+            let distance = distance_segment_to_point(p, pp, point);
+            if distance < width {
+                return true;
+            }
+        }
+        previous_point = Some(p);
+    }
+    false
+}
+
+/// rotates vector by angle
+fn rotate_vector(vec: Vec2, angle: f32) -> Vec2 {
+    let cos = angle.cos();
+    let sin = angle.sin();
+    Vec2::new(cos * vec.x - sin * vec.y, sin * vec.x + cos * vec.y)
+}
+
+/// finds point exactly in the middle between 2 points
+fn point_between(p1: Pos2, p2: Pos2) -> Pos2 {
+    let base = p1 - p2;
+    let base_len = base.length();
+    let dir = base / base_len;
+    p1 - (base_len / 2.) * dir
+}

src/main.rs

@@ -1,15 +1,18 @@
 use eframe::{run_native, App, CreationContext, NativeOptions, Frame};
 use egui::{CentralPanel, SidePanel, Context};
-use egui_graphs::{GraphView, Graph, SettingsStyle, LayoutRandom, LayoutStateRandom};
+use egui_graphs::{DefaultEdgeShape, DefaultNodeShape, Graph, GraphView, LayoutRandom, LayoutStateRandom, SettingsStyle};
 
-use algorithms::ford_fulkerson;
+use petgraph::Directed;
 use random_generator::MaxflowProblem;
+use layout::CustomEdgeShape;
+use crate::algorithms::ford_fulkerson;
+
 mod random_generator;
 mod algorithms;
-mod graph;
+mod layout;
 
 pub struct MaxflowApp {
-    g: Graph<(f32, f32), (u64, u64)>,
+    g: Graph<(f32, f32), (u64, u64), Directed, u32, DefaultNodeShape, CustomEdgeShape>,
     p: MaxflowProblem,
     node_count: u64,
     max_capacity: u64,
@@ -26,7 +29,7 @@ impl App for MaxflowApp {
     fn update(&mut self, ctx: &Context, _: &mut Frame) {
         ctx.set_theme(egui::Theme::Light);
         CentralPanel::default().show(ctx, |ui| {
-            ui.add(&mut GraphView::<_, _, _, _, _, _, LayoutStateRandom, LayoutRandom>::new(&mut self.g).with_styles(&SettingsStyle::default().with_labels_always(true)));
+            ui.add(&mut GraphView::<_, _, _, _, _, CustomEdgeShape, LayoutStateRandom, LayoutRandom>::new(&mut self.g).with_styles(&SettingsStyle::default().with_labels_always(true)));
         });
         SidePanel::right("right_panel")
             .min_width(200.)

src/random_generator.rs

@@ -1,6 +1,6 @@
 use petgraph::stable_graph::{StableGraph, NodeIndex};
 use petgraph::{Directed};
-use egui_graphs::{Graph};
+use egui_graphs::{default_edge_transform, default_node_transform, to_graph_custom, DefaultEdgeShape, DefaultNodeShape, Graph};
 use egui::Pos2;
 use rand::thread_rng;
 use rand::Rng;
@@ -9,15 +9,18 @@ use itertools::Itertools;
 use geo::{Line, coord, line_intersection::{line_intersection, LineIntersection}};
 use egui::Color32;
 
+use crate::layout::CustomEdgeShape;
+
 pub struct MaxflowProblem {
-    pub g: Graph<(), u64, Directed, u32, egui_graphs::DefaultNodeShape, egui_graphs::DefaultEdgeShape>,
+    pub g: StableGraph<(f32, f32), (u64, u64)>,
     pub s: NodeIndex,
     pub t: NodeIndex,
 }
 
 impl MaxflowProblem {
     pub fn new(num_nodes: u64, max_capacity: u64) -> Self {
-        let mut graph: Graph<_, u64> = Graph::new(StableGraph::default());
+        // Node Type: (x,y) Edge Type: (current_flow, capacity)
+        let mut graph: StableGraph<(f32, f32), (u64, u64)> = StableGraph::default();
         let mut nodes: Vec<NodeIndex> = Vec::new();
         let mut rng = thread_rng();
 
@@ -25,30 +28,27 @@ impl MaxflowProblem {
         for _i in 0..num_nodes {
             let x: f32 = rng.gen_range(0.0..=400.0);
             let y: f32 = rng.gen_range(0.0..=300.0);
-            let pos = Pos2::new(x,y);
+            let n = graph.add_node((x,y));
-            let n = graph.add_node_with_label_and_location((), String::new(), pos);
             nodes.push(n);
         }
 
         // select source (s) and sink (t)
-        let s = *nodes.choose(&mut rng).expect("no nodes found");
+        let (s,t) = nodes.choose_multiple(&mut rng, 2).copied().collect_tuple::<(NodeIndex, NodeIndex)>().expect("not enough nodes");
-        let t = *nodes.choose(&mut rng).expect("no nodes found");
-        graph.node_mut(s).expect("node index not found").set_label(String::from("s"));
-        graph.node_mut(t).expect("node index not found").set_label(String::from("t"));
-        graph.node_mut(s).expect("node index not found").set_color(Color32::RED);
-        graph.node_mut(t).expect("node index not found").set_color(Color32::GREEN);
 
         // iterate over all possible edges
         let mut possible_edges: Vec<(NodeIndex, NodeIndex, f32)> = Vec::new();
         for pair in nodes.clone().into_iter().combinations(2) {
             // calculate distance & append tuple (node_a, node_b, distance) to possible_edges
-            let distance = Self::distance(graph.node(pair[0]).expect("node index not found").location(), graph.node(pair[1]).expect("node index not found").location());
+            let distance = Self::distance(
+                *graph.node_weight(pair[0]).expect("node index not found"),
+                *graph.node_weight(pair[1]).expect("node index not found")
+            );
+            //let distance = Self::distance(graph.node(pair[0]).expect("node index not found").location(), graph.node(pair[1]).expect("node index not found").location());
             possible_edges.push((pair[0], pair[1], distance));
         }
 
         // sort mapping by distance
         possible_edges.sort_by(|a, b| a.2.partial_cmp(&b.2).unwrap());
-        println!("possible_edges len: {}", possible_edges.len());
 
         // insert the edge if possible
         let mut inserted_edges: Vec<(NodeIndex, NodeIndex)> = Vec::new();
@@ -57,10 +57,10 @@ impl MaxflowProblem {
             let mut intersects = false;
             for (node3, node4) in &inserted_edges {
                 if Self::intersects(
-                    graph.node(node1).expect("node index not found").location(),
+                    *graph.node_weight(node1).expect("node index not found"),
-                    graph.node(node2).expect("node index not found").location(),
+                    *graph.node_weight(node2).expect("node index not found"),
-                    graph.node(*node3).expect("node index not found").location(),
+                    *graph.node_weight(*node3).expect("node index not found"),
-                    graph.node(*node4).expect("node index not found").location(),
+                    *graph.node_weight(*node4).expect("node index not found"),
                 ) {
                     intersects = true;
                     break;
@@ -71,29 +71,54 @@ impl MaxflowProblem {
                 inserted_edges.push((node1, node2));
                 inserted_edges.push((node2, node1));
                 let capacity: u64 = rng.gen_range(1..=max_capacity);
-                graph.add_edge_with_label(node1, node2, capacity, capacity.to_string());
+                graph.add_edge(node1, node2, (0, capacity));
-                graph.add_edge_with_label(node2, node1, capacity, capacity.to_string());
+                graph.add_edge(node2, node1, (0, capacity));
             }
         }
 
         Self { g: graph, s: s, t: t }
     }
 
+    pub fn from(g: StableGraph<(f32, f32), (u64, u64)>, s: NodeIndex, t: NodeIndex) -> Self{
+        Self {g: g, s: s, t: t}
+    }
+
     // returns the eudclidean distance between two points
-    fn distance(a: Pos2, b: Pos2) -> f32 {
+    fn distance(a: (f32, f32), b: (f32, f32)) -> f32 {
-        let delta_x = a.x - b.x;
+        let delta_x = a.0 - b.0;
-        let delta_y = a.y - b.y;
+        let delta_y = a.1 - b.1;
         return f32::sqrt(delta_x.powf(2.) + delta_y.powf(2.));
     }
 
     // checks if the lines between a-b and c-d intersect
-    fn intersects(a: Pos2, b: Pos2, c: Pos2, d: Pos2) -> bool {
+    fn intersects(a: (f32, f32), b: (f32, f32), c: (f32, f32), d: (f32, f32)) -> bool {
-        let line1 = Line::new(coord! {x: a.x, y: a.y }, coord! {x: b.x, y: b.y  } );
+        let line1 = Line::new(coord! {x: a.0, y: a.1 }, coord! {x: b.0, y: b.1  } );
-        let line2 = Line::new(coord! {x: c.x, y: c.y }, coord! {x: d.x, y: d.y  } );
+        let line2 = Line::new(coord! {x: c.0, y: c.1 }, coord! {x: d.0, y: d.1  } );
         match line_intersection(line1, line2) {
             // only return true for 'proper' intersections which are not at the end of a line
             Some(LineIntersection::SinglePoint { is_proper: true, .. }) => true,
             _ => false
         }
     }
+
+    pub fn to_gui_graph(&self) -> Graph<(f32, f32), (u64, u64), Directed, u32, DefaultNodeShape, CustomEdgeShape> {
+        let mut graph = to_graph_custom(&self.g,
+            |n| {
+                let (x, y) = *n.payload();
+                default_node_transform(n);
+                n.set_location(Pos2::new(x, y));
+                n.set_label(String::from(""));
+            },
+            |e| {
+                let (flow, capacity): (u64, u64) = *e.payload();
+                default_edge_transform(e);
+                e.set_label(format!("{flow}:{capacity}"));
+            }
+        );
+        graph.node_mut(self.s).expect("node index not found").set_label(String::from("s"));
+        graph.node_mut(self.t).expect("node index not found").set_label(String::from("t"));
+        graph.node_mut(self.s).expect("node index not found").set_color(Color32::RED);
+        graph.node_mut(self.t).expect("node index not found").set_color(Color32::GREEN);
+        graph
+    }
 }